After days of headlines proclaiming that bacon and hot dogs cause cancer following the World Health Organization's (WHO's) classifying processed meat as a human carcinogen ― in the same category as tobacco and asbestos ― the WHO released a statement in clarification. It pointed out that the latest report from the International Agency of Cancer Research (IACR), issued last week, "does not ask people to stop eating processed meats"; rather, it indicated "that reducing consumption of these products can reduce the risk of colorectal cancer."

The WHO also published online a question-and-answer document and tweeted large parts of this in an attempt to present the facts ― but it was a little after the event, coming 4 days after the IACR report had been published, after headlines worldwide had demonized bacon and sausages, and after the Twitter hashtag #JeSuisBacon had been trending.

A major point made in the WHO Q&A document is that although processed meats have now been classified as carcinogenic to humans (IACR Group 1), and although this category also includes tobacco and asbestos and other substances, the WHO pointed out that the substances in this classification are not "all equally dangerous."

"The IARC classifications describe the strength of the scientific evidence about an agent being a cause of cancer, rather than assessing the level of risk," it added.

In other words, hot dogs and cigarettes present different risks, a fact not entirely clear when the report, which has been dubbed "Bacon-gate," was issued.

According to the most recent estimates by the Global Burden of Disease Project, an independent academic research organization, about 34,000 cancer deaths per year worldwide are attributable to diets high in processed meat; red meat could be responsible for 50,000 cancer deaths per year worldwide.

In contrast, about 1 million cancer deaths per year globally are due to tobacco smoking, 600,000 per year are due to alcohol consumption, and more than 200,000 per year are due to air pollution, the WHO points out.

The WHO also repeated the estimates presented by the IACR in its report, saying that every 50-g portion of processed meat eaten daily increases the risk for colorectal cancer by about 18%, and that 100 g of red meat could increase the risk for colorectal cancer by 18%.

It did not, however, emphasize that these are relative risks. That was left to others.

Cancer Research UK (CRUK), in a scienceblog, used UK population data to give some absolute numbers.

In the United Kingdom, colorectal cancer affects about 61 of every 1000 people. Those who eat the lowest amount of processed meat are likely to have a lower lifetime risk than the rest of the population (about 56 cases per 1000 people who eat little or no meat). Those who eat the most processed meat would have an increased risk (about 66 cases per 1000 people).

CRUK also issued a graphic (reproduced below) to illustrate how the risk for cancer from eating processed meat and red meat compares with the risk from smoking tobacco.

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